Tracer material for missiles



June 1964 o. B. HANSSON ETAL 3,135,201

TRACER MATERIAL FOR MISSILES Filed March 29, 1961 F 2 mm mm, Mmzw KARLELOV Lb'F-STEDT' HEM) TDQSTEN N/LS-GUNMR NEDEBY A Transm- United StatesPatent 3,135,201 TRACER MATERIAL FGR MISSILES Oscar Bernhard Hansson andKarl Elov Liifstedt, Rotors,

and Henry Torsten Nils-Gunnar Nedeby, Karlskoga,

Sweden, assignors to Airtiebolaget Bofors, Bofors,

Sweden, a corporation of Sweden Filed Mar. 29, 1961, Ser. No. 99,150Claims priority, application Sweden Apr. 14, 1960 Claims. (Cl. 102-375)The present invention relates to light generating tracer material forinsertion in or attachment to a missile to facilitate visual tracing ofthe trajectory of the missile when the same is propelled by means of asuitable weapon.

Tracer materials of this kind are heretofore known to have a shortburning time-about 5-10 secondsand generate a substantially constantlight output while being consumed. As is Well known, the intensity oflight incident upon the eyes of an observer stationed for instance nearthe point from which the missile, including the tracer material, ispropelled decreases by the square of the distance from the observer. Dueto the constant light output of the tracer material, the intensity ofthe light as seen by such observer is excessively strong during thefirst part of the trajectory, but becomes rapidly too faint for reliableobservation as the missile moves further away from the observer,particularly since the observer tends to be momentarily blinded by theinitial high brilliancy of the tracer light. Attempts have been made touse a delay composition causing the tracer material to become ignitedonly after a certain distance of flight, but this entails the dangerthat the specific missile which the observer wants to observe cannot belocated within the available short period of time. Furthermore, theeffect of the delay composition does not eliminate the problem, but atbest mitigates it.

It is the broad object of the invention to provide a novel and improvedtracer material of the general kind above referred to which has for agiven volume of material, a longer burning time than heretoforeobtainable and a light output which increases during the burning of thetracer material. Such combination of features affords the advantage thatthe missile bearing the tracer material can be observed for a greaterpart of its trajectory and that the danger of a temporary blinding ofthe observer by an initial excessive brilliance of the tracer light iseliminated, or at least reduced.

The use of tracers according to the invention is particularlyadvantageous in conjunction with manually remote-controlled,rocket-motor driven, armor-piercing projectiles. Such projectiles have acomparatively low velocity, which makes a prolonged burning timeparticularly useful, and having a rather flat trajectory which oftennearly coincides with the usual sighting line, thus making an initialstrong glare particularly troublesome.

A more specific object of the invention is to provide a novel andimproved tracer in which the luminous material is so shaped that themaximum light output is attained therefrom.

Luminous compositions used as tracer materials usually comprise amixture of magnesium, an oxydizing agent, a desensitizing agent and abinder. It has been found that the intensity of the light output of suchmixture can be increased by reducing the relative proportions of thedesensitizing agent and the binder in the mixture, but such increase inintensity is obtained at the expense of the burning time. The inventionutilizes the afore-described phenomenon by combining in a tracer aplurality of compositions which have different burning times anddifferent light-emitting properties and arranging these compositions sothat the composition having the longest burning time and the lowestlight emission is burned first and the composition having the shortestburning time and the highest light emission is burned last. By selectingthe mass of each composition appropriately, a tracer charge is obtainedwhich has a long total burning time and the light output of whichincreases towards the end of the burning time, whereby the lightintensity of the tracer as seen by a stationary observer remainsapproximately constant.

Other and further objects, features and advantages are pointed outhereinafter and set forth in the appended claims constituting part ofthe application.

In the accompanying drawing, a preferred embodiment of the invention isshown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a sectional view of a tracer according to the invention, and

FIG. 2 is a graph showing comparative light intensitytime curves oftracer materials.

Referring first to FIG. 1 in detail, the entire tracer charge is placedin a cylindrical can 1 open at one end and made of suitable materialsuch as steel. The inside of the can is lined with a liner 2 made of amixture of hardening plastic and glass powder.

The tracer charge is a composite charge made up of a plurality oflayers, some serving as primers and others as light generating layers.

More specifically, layer 3 is a black powder priming charge.

Layer 4 is a priming charge having a composition of 59% of bariumperoxide, 36% of stannic oxide and 5% of chlorinated rubber. Suchcomposition does not produce any appreciable light when burned.

Layer 5 is a composition consisting of 35% of the composition of layer 4and of 65% of a light generating tracer composition comprising 64.7% ofstrontium nitrate, 8.8% of strontium chloride, 11.8% of magnesium, 8.8%of polyvinyl chloride and 5.9% of chlorinated rubber.

Layer 6 is a light generating composition consisting entirely of thetracer material composition used for layer 5 in a proportion of 65% ofthe total mass of that layer.

Layer 7 is a light generating composition consisting of 64.7% ofstrontium nitrate, 5.9% of strontium chloride, 17.6% of magnesium, 5.9%of polyvinyl chloride and 5.9% of chlorinated rubber.

Finally, layer 8 is also a light generating composition consisting of58.8% strontium nitrate, 29.4% of magnesium, 5.9% of polyvinyl chlorideand 5.9% of chlorinated rubber.

The aforelisted compositions are placed in the can in reverse order inrelation to the desired ignition sequence thereof. As shown in FIG. 1,layer 8, which produces the highest light intensity and has the shortestburning time, is at the bottom, thus it will burn last, and primingcomposition 3 is at the top of the can at which combustion of the tracermaterial is started. FIG. 1 further indicates by the spacing of thelines indicating the layers that the layers have different volumes. Theproportion of the volumes of the layers is selected in accordance withthe desired distribution of the light output during the flight of themissile and the desired total burning time.

The compositions are pressed together successively by any suitablemeans, such as a cylindrical punch. The punch has preferably a conicalpoint to obtain the illustrated conical mating surfaces of the layers.As has been pointed out before, a more uniform increase of the intensityof the light output as the consumption of the tracer material progressesfrom layer to layer, is obtained by the illustrated conical shape.

FIG. 2 shows light intensity 0 as a function of the burning time h. Thecurve 9 indicates the light intensity of tracer material according tothe invention. As shown,

the tracer material reaches rather rapidly its peak intensity and thenremains substantially constant as seen by a stationary observer.

Curve shows the actual light intensity of the tracer material accordingto the invention. light intensity increases during the burning time ofthe tracer material.

Finally, curve 11 shows the light intensity of conventional tracermaterial. The curve indicates that the light intensity reaches rapidly ahigh peak and then decreases equally rapidly. The peak being located atthe beginning of the total time causes the aforementioned temporaryblinding of an observer. A comparison of curves 9, 10 and 11respectively also demonstrates the much longer burning time of thetracer material according to the invention, for a given total volume oftracer material.

While the invention has been described in detail with respect to acertain now preferred example and embodiment of the invention, it willbe understood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A luminous tracer for use with a missile, comprising a container,tracer material of a plurality of combustible, light-generatingcompositions in said container, said compositions having differentburning times for a given mass and generating light of differentintensities when ignited, the burning time and the light intensities ofthe compositions being inversely proportional, said compositions beingstacked in said container to form a column in which the compositions aresuperimposed in an order such that the composition having the longestburning time and generating the lowest light intensity is located at oneend of the column and the composition having the shortest burning timeand generating the highest light As is apparent, the

intensity is located at the other end thereof, and a priming chargedisposed in said container adjacent the composition having the longestburning time and generating the lowest light intensity, whereby uponignition of the Y column at the end thereof including the compositionhaving the longest burning time and generating the lowest lightintensity, the intensity of the light emitted by the tracer materialincreases as the consumption thereof progresses toward the other end ofthe column so that the light intensity of the tracer as the time anddistance of flight of the missile increases provides a light intensitywhich, as seen by a stationary observer, remains approximately constant.

2. A tracer material according to claim 1 wherein the facing surfaces of:adjacent compositions are slanted in reference to the center axis ofsaid column.

3. A tracer material according to claim 1 wherein the facing surfaces ofadjacent compositions have a conical configuration, the splices of theconical surfaces being aligned along the center axis of the column.

4. A tracer material according to claim 1 wherein said container has anopen end, the composition generating the lowest intensity of light beinglocated at the open end of said container.

5. A tracer material according to claim 1 wherein the priming charge isplaced upon the outer side of said composition at the open end of saidcontainer.

References Cited in the file of this patent UNITED STATES PATENTS1,074,809 Newton Oct. 7, 1913 1,920,075 Haenichen July 25, 19332,868,129 Johnson et al. Jan. 13, 1959 2,986,999 Fiedler et al. June 6,1961 3,013,495 Stevenson et al. Dec. 19, 1961 FOREIGN PATENTS 219,177

Switzerland May 1, 1942

1. A LUMINOUS TRACER FOR USE WITH A MISSILE, COMPRISING A CONTAINER,TRACER MATERIAL OF A PLURALITY OF COMBUSTIBLE, LIGHT-GENERATINGCOMPOSITIONS IN SAID CONTAINER, SAID COMPOSITIONS HAVING DIFFERENTBURNING TIMES FOR A GIVEN MASS AND GENERATING LIGHT OF DIFFERENTINTENSITIES WHEN IGNITED, THE BURNING TIME AND THE LIGHT INTENSITIES OFTHE COMPOSITION BEING INVERSELY PROPORTIONAL, SAID COMPOSITIONS BEINGSTACKED IN SAID CONTAINER TO FORM A COLUMN IN WHICH THE COMPOSTION ARESUPERIMPOSED IN AN ORDER SUCH THAT THE COMPOSITION HAVING THE LONGESTBURNING TIME AND GENERATING THE LOWEST LIGHT INTENSITY IS LOCATED AT ONEEND OF THE COLUMN AND THE COMPOSITION HAVING THE SHORTEST BURNING TIMEAND GENERATING THE HIGHEST LIGHT INTENSITY IS LOCATED AT THE OTHER ENDTHEREOF, AND A PRIMING CHARGE DISPOSED IN SAID CONTAINER ADJACENT THECOMPOSITION HAVING THE LONGEST BURNING TIME AND GENERATING THE LOWESTLIGHT INTENSITY, WHEREBY UPON IGNITION OF THE COLUMN AT THE END THEREOFINCLUDING THE COMPOSITION HAVING THE LONGEST BURNING TIME AND GENERATINGTHE LOWEST LIGHT INTENSITY, THE INTENSITY OF THE LIGHT EMITTED BY THETRACER MATERIAL INCREASES AS THE CONSUMPTION THEREOF PROGRESSES TOWARDTHE OTHER END OF THE COLUMN SO THAT THE LIGHT INTENSITY OF THE TRACER ASTHE TIME AND DISTANCE OF FLIGHT OF THE MISSILE INCREASES PROVIDES ALIGHT INTENSITY WHICH, AS SEEN BY A STATIONARY OBSERVER, REMAINSAPPROXIMATELY CONSTANT.